Field of the Invention
The present invention relates to a stepping motor and a motorized valve using it.
Description of the Conventional Art
Conventionally, in a motorized valve using a stepping motor, for example, reliable base point positioning of the stepping motor (it is also called initializing) is guaranteed by inputting a drive pulse signal which is over the maximum step numbers necessary to close the motorized valve. For example, Japanese Patent Application Laid-Open No. 2005-287152 discloses a solenoid coil device of a stepping motor of such a motorized valve. In this conventional technique, exciting coils, in which a pair of magnetic pole plate (magnetic pole teeth) is provided from the top and bottom inside thereof, are provided in the two-tiered up and down.
On the other hand, it has been known that some problems generate when continuing to input the drive pulse signal to a stepping motor after a rotor constituting the stepping motor is stopped by a stopper, or the like, at a base point position. These problems are generating of noise or vibration, and lowering of durability of the stepping motor.
For solving these problems, Japanese Patent No. 4,028,291 discloses a technique detecting contact of a rotor to a stopper at a time of the base point positioning of the stepping motor, and stopping the base positioning pulse energizing the drive coil.
In the drive device of the motorized valve disclosed in Japanese Patent No. 4,028,291, at a time of base point positioning of the motorized valve, the device outputs base point positioning pulse to the drive coil of a stator so as to return the rotor of the stepping motor to the base point position. At the same time, the device inputs a magnetic detection signal from a magnetic detection means. Then, the device recognizes a changing pattern of the magnetic detection signal corresponding to the difference of timing between when the stopper contacts and when the magnetic detection signal transfers from high level to low level or low level to high level. Then, the device detects the contact of the rotor to the stopper in the step corresponding to the changing pattern, and stops the pulse output for base point positioning.